Protection of water supplies from either inadvertent or deliberate contamination is an increasingly important concern. While there exist many different devices and methods to analyze water for contaminants, widespread deployment of such devices is expensive and difficult.
Most water treatment and distribution systems rely on the introduction and maintenance of a disinfectant into the water system to protect against biological and to a big extent chemical contamination. Chlorine, in the form of gas or hypochlorite, is by far the most common material used for this purpose. However, substitutes such as chloramines, ozone, hydrogen peroxide, peracetic acid, chlorine dioxide, and various mixed oxides also find service in this application. All of these materials have a more or less common mode of action. They rely on some sort of oxidation to effect the deactivation of biological organisms and the destruction of other organic compounds present in the water to be treated. The reaction rates of the various disinfection compounds are reasonably well known and well characterized.
Additionally, the presence or absence of turbidity in the water supply can greatly affect the amount of disinfectant required to achieve inactivation of biological organisms. The suspended particles producing turbidity are usually removed in the water treatment process before disinfection agents are applied. However, turbidity breakthroughs do occur and failure to quickly raise the disinfection dose level can lead to insufficient disinfection residuals reaching the distribution system. This can present a threat to public health, particularly if the drinking water supply is contaminated either deliberately or inadvertently.
To respond to the threats of terrorism in drinking water supplies, sensors have been and are being introduced into the distribution system to continuously monitor selected contaminants in the drinking water supply. For example a system may monitor free chlorine residual at a location in the distribution system downstream of the main treatment plant. However, the concentration of free chlorine present at this point in the distribution system may lag the free chlorine analyzed at the exit of the water treatment plant by hours or even days in some cases. The lag will also vary by time of day, since water demand follows well known 24 hour cyclical periods.
Applicant's invention registered as U.S. Pat. No. 6,332,110 teaches the use of a remote monitoring system to monitor the performance of an advanced separation process, particularly as related to water treatment. Many of the analytical devices used to continuously monitor water treatment operations are based on advanced separation processes employing selective ion membranes which concentrate the analyte for the detector apparatus. For example, detection of chlorine may be mediated via a membrane which readily and specifically passes free chlorine or hypochlorous acid (HOCl), thus separating the analyte from the bulk solution and concentrating it. The detector apparatus may incorporate multiple sensors and analyzers on a single unit. The multiple units are usually electronically controlled. The control system usually features output methods allowing the display and storage of collected data.
Deploying a range of sensor systems in the field provides a means to analyze for contaminants but does not provide for reporting and subsequent analysis of the data. Rapid reporting of the data to a facility readily accessible by the management or operators of the utility or distribution system and subsequent analysis of the data is very important to providing quick response in the event of a system contamination, either deliberate or otherwise.
The instant invention provides a means of rapidly aggregating the information at a central location in a form readily accessible to authorized users such as Homeland Security. It further provides a means to employ sophisticated statistical and data analysis techniques to the collected data. Since the central data collection server is connected to the internet, dispersion of alarms and alerts is greatly facilitated.
This invention consists of a method for collecting analytical data from the electronic control system of a single analyzer unit or multiple analyte units, storing the raw data locally for a short period of time, and subsequently using any of a variety of transmission means to send this data to a remote internet server computer. At the remote internet server computer, the data is stored in a database and may also be displayed via a web server. Upon arrival, or upon scheduled intervals, or upon a user request, the data is analyzed, compared to historical records, and a performance analysis result is made. Based upon the raw data or upon the analysis result, reports can be issued to appropriate regulatory agencies, alerts or alarms can be raised, and notifications issued via email, pager, voice or text messaging, or other messaging medium which can be mediated by a computer program connected to a phone line or the internet.
The methods used for data analysis can be readily varied or modified by someone skilled in the art of computer programming since the raw data is easily available from the database for manipulation. For example, the analytical data, when combined with known system constants such as flow rates, residence times, and so on, can be used to continuously generate a calculated product of disinfectant concentration times contact time C*T. This simple factor alone is quite useful in predicting the amount of biological organism deactivation. More sophisticated analyses can also be utilized. The results can be conveniently stored in the database and displayed as virtual sensors.
This invention is particularly useful when the same remote server computer has access to data from both the treatment facility and to analytical data from within the distribution system. In this case, historical information can be used to predict the expected conditions within the distribution system based on the effluent conditions from the treatment plant. The expected conditions can then be compared to the actual conditions in the distribution system. For example, in the instant invention, assume that data is being collected at the water treatment plant from the electronic control system about water flow rates, chemical dosing rates, filtered water turbidity, and chlorine residual. Also assume that data is also being collected from sensors in the distribution system reporting chlorine residual among other data. With current data and with historical data as a reference point, one can calculate a chlorine demand from the chemical dose rates, flows, and residual. Chlorine Demand is the actual amount of chlorine which is reacting, typically calculated as free chlorine dosed less the residual. Chlorine demand can be correlated with temperature, season, and filtered water turbidity. Additionally residual chlorine leaving the plant can be correlated with residual chlorine within the distribution system. If the actual chlorine residual measured at the distribution system point of measurement varies from the historical values expected from the chlorine residual leaving the treatment facility by more than a set percentage or more than a set number of standard deviations, then an alarm or alert may be issued by the monitoring system of the instant invention.
As a further example, consider the potential deliberate injection of chemically or biologically active agents into the distribution system at a point downstream of the treatment facility. A sophisticated terrorist may first inject a chlorine scavenger such as sodium metabisulfite into the distribution system to eliminate the chlorine residual normally present. At some point downstream of the metabisulfite injection point, the chemical or biological agent can be injected into the water without destruction by any residual disinfectant. Without an analytical station and monitoring system in place within the distribution system this approach could go undetected for quite some time, allowing a thorough infiltration of a biological or chemical agent throughout the distribution system. Assuming such an attack, the chlorine residual at the monitoring station would very quickly diminish to zero. A monitoring system with an active system in place to analyze the incoming data would quickly detect such an attack and sound the alarm. With historical data to compare to, the incidence of false terrorist attack alarms could be greatly diminished. For example a chlorine dosing equipment failure would be noticed at the water treatment plant providing information that a subsequent fall of chlorine concentration in the distribution system was not a terrorist attack, but an equipment failure.
In the same example of a hypothetical terrorist attack, the terrorist might try to simply overwhelm the residual chlorine in the distribution system by injecting, for example, an amount of biological or chemical agent dispersed as a fine powder in water. In this case, chlorine would fall as well but depending on the location of the sensors in relation to the injection point, the concentration might not fall to zero. However, the turbidity might well be affected. Thus a turbidity sensor in the distribution system would be an advantage in assessing a potential threat. In all cases, the need to quickly transmit raw data from both the distribution system and treatment plant to a computer system where it can be manipulated and analyzed is very important for prompt action to occur in response to any threat to the water system.